Title: From Biological to Social Processes: Interdisciplinary Training in Life Course Research The poor overall health status of the US population in comparison with our high-income peers and the staggering gaps in key measures of health and well-being by socioeconomic status and race/ethnicity across the life course highlight the urgency at which we must address the factors and mechanisms that lead to poor health outcomes. At the same time, it has become ever more apparent that the scientific paradigms and research approaches of today have not effectively addressed the complex constellation of factors that fundamentally influence US health and well-being from birth through adulthood. For these reasons, the National Institutes of Health has called for novel integrative research, from cells to society, to better address the web of factors that cause persistent health inequalities and result in relatively poor overall levels of health in society. Nonetheless, there is a major gap in interdisciplinary training in US universities, partly because of disciplinary silos, lack of initiative, and historical distinctions on campuses. We propose an innovative training program that will produce highly trained interdisciplinary pre- and post-doctoral trainees entering from either the social sciences or biological/health sciences who will be able to conduct integrative work across these areas that will address some of the country's most pressing health problems. With training focused on gaining knowledge from a new area of study, enhancing interdisciplinary interactions and exchange, and integrative research production, we envision that these pioneering trainees will be more likely to develop into creative and flexible scientists whom are able to develop new research pathways and create the innovative unifying frameworks that arise from crossing disciplinary boundaries. To enhance training experiences, multidisciplinary exchange, and ultimately integration of biological/health and social approaches, we seek support for eight pre- doctoral trainees (four from the biological/health sciences and four from the social sciences annually) and two post-doctoral trainees (one from each of the social and biological/health sciences). With substantial guidance from the program directors and their cross-disciplinary mentors, trainees will develop individually tailored training tracks in either the social sciences or biological/health sciences, with the track tailored to prior disciplinary training and each trainee's research interests. Social science students and post-docs will develop a biological/health sciences gap training track in one of three areas: 1) genetics; 2) cardiovascular and metabolic; 3) immunology, infections, and microbiome), while biological/health science students and post-docs will develop a social science gap training track in one of three areas: 1) social inequality; 2) socio-spatial organization and processes; 3) age-period-cohort. With this program, we aim to create junior scientists who are able to conduct cutting edge integrative social and biological/health sciences research and who will be future leaders who will use these new approaches to improve human health and well-being in the US and beyond.